Compressor stator assembly



April 1960 c. NEUMANN 2,933,234

COMPRESSOR STATOR ASSEMBLY Filed Dec. 28. 1954 2 Sheets-Sheet 1INVENTOR. 6264459 WfVA/i/V/V #44 Mama-7 April 1960 G. NEUMANN 2,933,234

COMPRESSOR STATOR ASSEMBLY Filed Dec. 28, 1954 2 Sheets-Sheet 2 1E4 L IINVENTOR. 6564450 A fMI/i/V/Y apd $7.

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COP/ERESSOR STATOR ASSEMBLY Gerhard Neumann, Cincinnati, Ohio, assignorto General Electric Company, a corporation of New York ApplicationDecember 28, 1954, Serial No. 478,100

6 Claims. (Cl. 230-114) This invention relates to stator vanes in acompressor for a gas turbine engine or the like, and, in particular, toa means for varying the position of the stator vanes in the compressor.

Wherever high pressure ratio compressors of the axial flow type areused, aerodynamic stall conditions exist at some period when going fromzero speed to maxi- It has been found that the higher the pressureratio, the more pronounced the stall conditions become. This stallcondition exists as a result of the flow failing to match theaerodynamic design of the blading itself. In other words, the angle ofattack is too high. Therefore, in order to correct for these stallconditions, the positions of the stator vanes are varied by changing theangle of attack to meet the flow conditions over a wide range ofoperating conditions. 7

It is well known that stator vanes are attached to the compressor casingat one end thereof, and, therefore act as cantilever beams. These statorvanes are subjected to extremely heavy loads and vibratory forces. Itis, therefore, an object of this invention to provide a wide basesupport that is capable of maintaining a stator vane in a firm conditionand still be easily rotatable. For this invention, a wide base supportor shoulder is intended to cover a base which is relatively large indiameter with respect to the chord of the vane.

The compressor casing is often made of a relatively thin construction tohold its outside diameter to a minimum. In order to provide a supportfor the vanes the casing must be built up, thereby increasing the weightof the engine and reducing the advantages of the variable stator vaneengine. Accordingly, it is a further object of this invention to make alight weight, shallow support that is capable of maintaining the bladein a firm condition without affecting its rotatability.

In order to make the stator blades of a compressor variable, the basesof the blades are actuated by levers which in turn are actuated by acircumferential band extending about the circumference of thecompressor. Since the levers pivot in a plane tangential to thecircumference of the actuator band, a problem arises as to how toconnect the actuator band to the levers. It is therefore a specificobject of this invention to provide a connection between the actuatorband and levers which will permit them to turn in different planes, withthe actuator band being constrained in an axial direction.

One of the most sought for features in a jet engine is lightness ofparts. It is therefore another specific object of tlL's invention toprovide fabricated lightweight levers and bases for the stator vaneswith a runner mounted on the actuator bands and a sector on thecompressor casing provided with anti-friction material to support therunner and for supporting the levers so as to maintain the vibratoryforces at a minimum.

It is a more specific object of this invention to provide the compressorof a jet engine ith a variable stator mechanism by having the base ofthe stator vanes rotatable in a flat bearing in the compressor casing,the

base of the blades being fabricated for lightness.

Fabricated lever arms are connected to the bases 'of the blades so as tobe rotatable therewith, the levers being pivotally connected to actuatorbands through a ball and socket joint, the levers having rod endsslidably positioned in the ball. The actuator bands are supported on thecasing and constrained axially and actuated by hydaulically actuatedbellcranks having their fulcrums on the casing.

It is a still more specific object of this invention to provide alightweight variable stator blade assembly and lightweight lever foractuating the blade, the blade being fabricated so as to have a fiatbase and the lever being fabricated in a manner so as to be fixed to thefabricated base and carried by an actuator band, the blade assemblyhaving a portion fixed to the casing and the blade having a portionrotatable with respect to the casing.

These and other objects will become more apparent when read in the lightof the accompanying drawings and specification wherein like parts havethe same num bers and wherein the terms used for the individual partsare intended to be as generic in their application as the prior art willpermit, and wherein:

Figure 1 shows generally a gas turbine engine in which a variable statorvane construction is employed;

Figure 2 is a fragmentary plan view showing actuating means for movingthe actuating ring and brackets for rotating the vanes;

Figure 3 is a plan view, partly in section, showing the ball and socketjoint;

Figure 4 is a cross-sectional view taken on lines 4-4 ofFigure 2;

Figure 5 is a cross-sectional view taken on lines 5-5 ofFigure 2 showingthe ring supporting means;

Figure 6 is a cross-sectional view taken on lines 6-6 of Figure 5.

Referring to the drawings, and in particular to Figures 1-4, the numeralit generally designates a gas turbine engine provided with a compressorsection 12, combustor section 14, turbine section 16, and an exhaustnozzle section 18. A compressor casing 20 is provided with a pluralityof stator vanes rotatably mounted in the casing as will hereinafter bedescribed. Attached to the compressor casing 20 by rivets or the like 24are a plurality of sectors 22. The sectors 22 are spacedcircumferentially about the compressor casing 20. Fixedly mounted ineach sector 22 is a grooved member 23 made of a bearing material,such'as Teflon which is well known in the art and well adapted for thispur pose since it has good heat resistant and lubrication properties. AV-shaped runner 28 made of similar bearing material is adapted to slidein the corresponding groove 26 in the member 23. This runner 28 ismounted in an actuator band 30 by means of pins 29.

The actuator band 30, of which there is one for each stage of statorvanes, is adapted to be moved in either direction by a hydraulic pistonand cylinder arrangement 32 fixed to the compressor casing 26. Fixed tothe piston of this cylinder is a longitudinally extending bellcrank rod34 which carries a plurality of bellcranks 36 pivotally mounted on thebellcrank rod 34. The bellcranks are fixed at their fulcrum to thecompressor casing as shown at 38 equi-distant from the bellcrank rod 34.The bellcranks 36 are pivotally connected to the actuator bands 30 butthe arms of the bellcranks' are at varying distances for each stage, asis readily apparent by referring to Figure 2, according to apredetermined schedule. The actuator bands 3i) are provided withopenings 40 which extend through the sides thereof for the purpose whichwill be hereinafter explained. The actuator band 30, being of invertedU-shape is provided with a ball and socket arrangement as shown at 4-2.The ball contains an opening 44 therethrough for receiving a rod 46which is fixedly attached to a lever arm or bracket 48. The bracket 48is attached to the compressor blade assembly 4-7 and blade 50 by dowelpins 4g and screw 51 so as to rotate the blade.

The compressor-casing 24 is provided with a plurality of openings 52 forreceiving the compressor blade assembly 47. Fixed to the openings in thecompressor casing 20 is a sleeve 54 that may be either threaded or pressfitted into the opening 52. The compressor blade 50 is welded or brazedto the base or support 56. The base 56 is fabricated for lightness asshown in Figure 4. The base is formed by a cup-shaped member '3 with acover 55 also welded or brazed thereto. The cup-shaped member 53 andcover 55 form a flat shoulder -50. The sleeve 54 has a flat bearing seat57. The base or support 56 is mounted in a flat bearing 58 ofanti-friction material, such as Teflon. This material completelysurrounds the base 56 above and below the shoulder 60. The bean'ngisheld in place by a lock ring 6-2 fixed in the sleeve 54. Therefore theflat shoulder or seat 60 is embedded between two flat sheets of bearingmaterial 58 and one cylindrical along the side of the flat shoulder,which bearing material is held between the abutments formed by the lockring 62 and the seat 57. It is noted that the three portions of beariugmaterial can be made integral in the form of a U-shaped ring.

The leakage of any of the motive fluid from the compressor will decreasethe efficiency and result in poor performance of the engine. maintainedbetween the blade assembly and compressor casing by providing a flatbearing seat 63 surrounding the opening 52 and a mating flat bearingseat 64 on the fixed slseve 54. It is noted that this arrangementprovides for ease of assembly of the blade assembly in the compressorcassing. Also, the Teflon surrounding the shoulder 69 on the wide base56 also acts as a seal to prevent leakage from the compressor.

In order to operate the stator vanes the piston and cylinder arrangement32 is operated so as to move the bellcrank rod 34 which in turn operatesthe bellcranks 36. Since the throw of the bell cranks for each stage isdifferent, the actuator bands 30' are moved by a differentpie-determined amount. Movement of the actuator band 3%} results in themovement of the lever arms 48. It is noted that the rod 46 is slidablymounted in the ball and socket arrangement 42 to permit'the turning ofthe bracket 48 without twisting even though the actuator band 3%) andlevers 48 turn in different planes. Since the bracket ts is fixed to theroot of the blade 50 through the dowel pins 49 and screw 51, the blade50 will turn a pre-determined amount. Further, since the lever arms 48-are of lightweight material, they are too flexible to operate without asupport on their outer ends. Therefore, the actuator bands 30 supportthelever arms Therefore, a close fit is at the rod portions 46 by havingthe actuator bands good sealing and lubricating properties as well astemperature qualities. Further, the connection between the lever armsand actuator band is such thatthey can move in difierent planes. Also,sections of runners are provided on the casing for carrying theactuatorbands which support the lever arms.

It is apparent that the above description has been given by way ofexplanation and not by way 'of limitation and that many modifications,improvements and changes may be made to the above structures withoutdeparting from the spirit and intent of this invention. All of suchmodifications and improvements are intended to be included within thescope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a compressor for a turbomachine comprising a casing, at least onestage of stator vanes rotatably mounted in the casing, lever arms fixedto the base of said stator vanes so as to turn therewith, an actuatorband. slidably mounted on said casing adjacent each stage of rotatablestator vanes, ball and socket arrangemeans in said actuator bandsopeningsin the ball portions, said lever arms having rod ends extendingaxially of the arms through the openings in said ball portions, theactuator bands having a runner and the casing having a sector thereonfor supporting the runner and actuator bands, anti-friction material onthe runner and sector constraining the actuator band in an axial direc-'tion while permitting the band to be actuated in a circumferentialdirection, and means for actuating the bands.

2. In a compressor for a turbomachine comprising a casing, at least onestage of stator vanes rotatably mounted in the casing, the bases of saidstator vanes each having a rotatable portion with a flat bearingsurface, sleeves mounted in said casing for receiving said bases, eachsleeve having a flat bearing seat surface, layer of anti-frictionmaterial positioned between the seat surface and the flat bearingsurface of the associated blade, lever arms fastened to the rotatableportion of the bases to as to turn therewith, actuator bands extendingabout the casing, balls rotatably mounted in the actuator bands, thelever arms having rod ends thereon extending through the balls, saidbands being actuated so as to turn said stator vanes.

3. In a turbomachine, a'casing, openings in the easing, a blade assemblyfixed in each opening, the blade assembly including a sleeve having afixed seat and a removable seat, a blade provided with a base having aflat shoulder which is located between the seats, and flat bearingmaterial positioned between each seat and the flat shoulder to permitthe blade to rotate with respect to, the sleeve, and means forsimultaneously rotating the blades.- I

4. Ina turbomachine, a casing, openings in the casing, a'bladeassembly-fixed in each opening, said blade assembly including a sleevehaving a fixed seat and a removable seat, a blade provided with a basehaving a flat shoulderwhich'is' located between the seats, andfiatbearing material positioned between each seat and the flat shoulder topermit the blade to rotate with respect to the sleeve, alever arm fixedto each blade base so as to rotate therewith, actuator bands slidablymounted on the casing, ball and socket joints in the actuator bands,said actuator bands being connected to the lever arms through the balland socketjoint to permit the band to rotate in an arc of a circle andthe lever arm to rotate in a plane tangent to the arc of the circle.

5. In a compressor for a gas turbine engine, comprising a casing,openings in the casing, bearing seats in said casing each surrounding anopening therein, a plurality of stator vanes mounted on said seats andextending through said'openings, the openings containing a'removableseat spaced from the seat in the casing, the base of each of the vanesforming a substantially wide shoulder, flat bearing material positionedbetween the spaced seats and wide shoulder on the base of each of thevanes, lever arms fixed to the stator vanes so as to rotate therewith,the lever arms being suificiently light so as to be flexible, bandactuators slidably mounted on the casing, said band actuators carryingthe lever arms, means on the band actuators to permit movement of thelever arms without twisting, and means for actuating the bands.

- 2,933,234 5 t 6. In a compressor for a gas turbine engine comprisingReferences Cited in the file of this patent a casing, a plurality ofopenings in the casing, spaced UNITED STATES PATENTS bearing seats ineach opening, a plurality of stator vanes each having a substantiallywide shoulder, the Wide shoul- 22,05 311 lePdrasslk 1942 der beingpositioned between the bearing seats, fiat bear- 5 9 W1,1de 1952 ingmaterial interposed between and bearing against the L29 2 Fellden Sept1953 seats and the wide shoulder, lever arms fixed to the vanes, L496Buckland Sept 1953 actuator bands slidably mounted on the casing, balland 2671634 Morley 1954 socket joints mounted in the actuator bands, theactuator FOREIGN PATENTS bands being connected to the lever arms throughthe ball 10 500 965 Great Britain Feb 20 1939 and socket joints topermit the actuator bands and lever 1 Great Britain h 1949 arms movedlfierent Planes- 701,576 Great Britain Dec. 30, 1953 1,022,629 FranceDec. 17, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No, 2333 234: April 19 1960 Gerhard Neumann It is herebycertified that error appears in the-printed specification of the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 4 lines 13 and M for "arrangemeans" read arrangements Signed andsealed this 29th day of November 1960.,

( SEA L) Attest:

KARL H. AXLINE ROBERT C. WATSON Commissioner of Patents AttestingOflicer

